JPWO2005036705A1 - Optical semiconductor substrate - Google Patents

Abstract

The substrate for optical semiconductors of the present invention comprises an insulating ceramic substrate, a metal layer provided on the insulating ceramic substrate, and provided on the metal layer, and the balance is substantially 50 wt% or more of Sn alone or Sn. In particular, a solder layer made of Au, and a protective layer made of Au or Ag provided on the solder layer and having a thickness of 0.01 μm or more and 1 μm or less. By using such an optical semiconductor substrate, the stress applied to the optical semiconductor is reduced as much as possible when bonding optical semiconductors that are prone to crystal defects due to slight stress or during subsequent use, thereby suppressing the occurrence of crystal defects. Can extend the service life.

Description

  The present invention relates to an optical semiconductor substrate used for mounting an optical semiconductor, and particularly has excellent bonding properties with an optical semiconductor, and relaxes the stress applied to the optical semiconductor when the optical semiconductor is bonded or used. The present invention relates to an optical semiconductor substrate capable of suppressing damage to an optical semiconductor that is also damaged by the above and extending its lifetime.

  An optical semiconductor substrate is used as a semiconductor laser element by mounting an optical semiconductor such as an optical pickup LD for CD (Compact Disc) or DVD (Digital Video Disk). FIG. 1 shows a configuration example of a semiconductor laser element.

  The semiconductor laser element 1 has a structure in which an optical semiconductor 2 such as a laser diode is mounted on an optical semiconductor substrate 3. The optical semiconductor substrate 3 is used for improving the heat dissipation and positioning of the optical semiconductor 2. A heat sink 4 made of copper or the like having good thermal conductivity is joined to the other surface of the optical semiconductor substrate 3 in order to efficiently release, for example, heat generated in the optical semiconductor 2 to the outside (for example, a patent) Reference 1).

  The optical semiconductor substrate 3 comprises, for example, an insulating ceramic substrate 5, a metal layer 6 formed thereon by a sputtering method or the like, and a solder layer 7 formed thereon, and the optical semiconductor 2 is composed of this solder. The layer 7 is used for bonding onto the optical semiconductor substrate 3 (see, for example, Patent Document 2).

  FIG. 2 shows a general relationship between the current of the optical semiconductor 2 and the optical output. Spontaneously emitted light is emitted until the light output reaches Pth, and laser oscillation (stimulated emission) occurs when the light output exceeds Pth. The current value at the start of laser oscillation is the threshold current Ith. Specifically, the current value at which the extension line of the current-light output line in the oscillation state intersects the X axis is the threshold current Ith. Can do. Further, the value of the forward current when the prescribed optical output Po is obtained is the operating current Iop.

  In general, unlike a silicon chip used for a transistor or the like, a crystal defect occurs in the optical semiconductor 2 due to a slight stress at the time of bonding to the optical semiconductor substrate 3 or at the time of use. When the crystal of the optical semiconductor 2 is prepared, stimulated emission occurs due to light emission recombination, and by applying an operating current Iop to the optical semiconductor 2, a prescribed optical output Po can be obtained over a long period of time. On the other hand, if there is even a slight crystal defect in the optical semiconductor 2, non-radiative recombination occurs at that portion, and a large amount of heat is generated without emitting light. This heat causes further crystal defects in the optical semiconductor 2 and causes non-radiative recombination. By repeating this process, the optical semiconductor 2 cannot obtain the prescribed optical output Po in a short period of time, and eventually does not emit light.

Specifically, the damage due to stress is described. For example, in a general transistor in which a silicon chip is bonded to an alumina substrate, the thermal expansion coefficient of alumina is about 7 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the silicon chip is It is about 3 × 10 ⁻⁶ / ° C., and it can be used without being damaged despite a large difference in thermal expansion coefficient. In addition, in the case where a silicon chip is bonded to a lead frame made of copper, the difference between the thermal expansion coefficients of the lead frame made of copper is about 17 × 10 ⁻⁶ / ° C., which is very large. Some can be used regardless.

On the other hand, in a general semiconductor laser element 1, for example, a laser diode bonded on a silicon substrate, the thermal expansion coefficient of the silicon substrate is about 3 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the optical semiconductor. Is about 4.2 × 10 ⁻⁶ / ° C., and even though the difference in thermal expansion coefficient is small and only a small amount of stress is generated, crystal stress is generated in the laser diode due to the stress and the life is shortened. End up. Further, even when an aluminum nitride substrate having a thermal expansion coefficient of approximately 4.6 × 10 ⁻⁶ / ° C., which is substantially equal to the thermal expansion coefficient of the laser diode, is used, it is generated due to a slight difference in thermal expansion coefficient. The stress may cause crystal defects in the laser diode and shorten the lifetime.

In particular, in recent years, the output of the optical semiconductor 2 has been increased in order to improve the performance of the device, and the light density at the end face of the optical semiconductor 2 has become excessive, generating a large amount of heat, causing excessive stress and damage. Therefore, it is important to prevent the damage.
JP-A-6-37403 (FIG. 11 etc.) Japanese Patent Laid-Open No. 2002-1000082

  As described above, crystal defects are generated in the optical semiconductor even by a slight stress, and the lifetime is shortened. For this reason, an optical semiconductor substrate on which the optical semiconductor is mounted is required to have a low stress applied to the optical semiconductor when the optical semiconductor is bonded or used thereafter, and to prevent crystal defects from being generated in the optical semiconductor. The present invention was made to solve such a problem, and suppresses the stress applied to the optical semiconductor when joining the optical semiconductor or during subsequent use, suppresses the occurrence of crystal defects in the optical semiconductor, An object of the present invention is to provide an optical semiconductor substrate capable of extending the lifetime.

  As a result of studying the substrate for optical semiconductors to suppress the generation of crystal defects that shorten the lifetime of optical semiconductors, the present inventors have found that conventional general Au (gold) -Sn (tin) solder is a silicon chip. Although it is difficult to damage even if a little stress is applied like this, it can be used enough for bonding, but even if it is a slight stress like an optical semiconductor, crystal defects occur and its life is shortened, but it is too hard to join, so an optical semiconductor It has been found that the stress generated during bonding and use cannot be sufficiently relaxed, and crystal defects occur in the optical semiconductor, resulting in a shortened life.

  Accordingly, the present inventors have studied the material and composition of the solder constituting the solder layer of the optical semiconductor substrate. As a result, a general Au—Sn solder is hard because it contains a large amount of Au at about 80% by weight. Therefore, stress generated at the time of joining or using an optical semiconductor cannot be sufficiently relaxed, and the optical semiconductor is It was found that crystal defects occurred and the lifetime was shortened. Then, as a result of increasing the Sn content in the Au—Sn solder, it was found that the hardness of the Au—Sn solder can be effectively reduced.

  However, it was found that when Au—Sn solder containing a large amount of Sn is used as the solder layer, the solderability is lowered. In the manufacture of a semiconductor laser device, it is required to shorten the bonding time of the optical semiconductor to the optical semiconductor substrate in order to improve the productivity. Such a decrease in solderability becomes an obstacle to improving the productivity. Furthermore, when the solderability is reduced, the thermal resistance is increased, and the heat transfer from the optical semiconductor to the optical semiconductor substrate is not sufficiently performed, which causes stress and causes crystal defects in the optical semiconductor, thereby shortening the life. I understood it.

  As a result of repeated studies on such a decrease in solderability, the present inventors have found that the decrease in solderability is due to a decrease in solder wettability due to an oxide film formed on the surface of the Au-Sn solder that is the solder layer. Further, it was found that the formation of this oxide film is due to the fact that the Au—Sn solder constituting the solder layer contains a large amount of Sn that is easily oxidized.

  As a result of researches to improve the decrease in solderability due to the formation of such an oxide film, the present inventors have found that the Au—Sn solder surface, which is a solder layer, is not oxidized and does not cause other adverse effects. It has been found that covering is effective, and as such, it is effective to form a protective layer made of Au (gold) or Ag (silver) (hereinafter simply referred to as a protective layer) on the surface. That is, Au and Ag are not oxidized, have a low electrical resistance, or can form a eutectic with Sn, which is a component of the solder layer, and hardly cause adverse effects. Therefore, the protective layer that covers the surface of the Au—Sn solder that is a solder layer It was found to be suitable for the formation of. It has also been found that by forming such a protective layer on the surface of the solder layer, it is not always necessary to include Au in the solder layer.

  In addition, when the influence of the thickness of the protective layer on the oxidation and solderability of the solder layer surface was examined, it was found that the oxidation and solderability of the solder layer surface changed abruptly depending on the thickness. That is, when the thickness of the protective layer is less than 0.01 μm, a portion where the surface of the solder layer is not sufficiently covered occurs, and it becomes difficult to join the optical semiconductor due to the oxide film formed by oxidizing this portion, In addition, it was found that when the optical semiconductor was joined, the thermal resistance of this portion was increased and stress was generated, crystal defects were generated in the optical semiconductor, and the lifetime was shortened.

  On the other hand, if the thickness of the protective layer exceeds 1 μm, the protective layer and the solder layer are not completely mixed during the heat treatment for bonding the optical semiconductor, so that the protective layer remains, and Au or Ag As a result, a high-concentration portion is generated, which makes it difficult to join the optical semiconductor. Further, after joining, the high-concentration portion of Au or Ag is hard, so the stress is not sufficiently relaxed, and crystal defects occur in the optical semiconductor. It was found that the lifetime was shortened.

  The present inventors have completed the present invention based on the above findings. That is, the substrate for optical semiconductors of the present invention includes an insulating ceramic substrate, a metal layer provided on the insulating ceramic substrate, and provided on the metal layer, and contains the balance of Sn alone or Sn at 50% by weight or more. Comprises a solder layer substantially made of Au and a protective layer made of Au or Ag provided on the solder layer and having a thickness of 0.01 μm or more and 1 μm or less.

FIG. 1 is a sectional view showing an example of a general semiconductor laser element.
FIG. 2 is a diagram showing a relationship between current-light output characteristics of a general semiconductor laser element.
FIG. 3 is a cross-sectional view showing an example of an optical semiconductor substrate of the present invention.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 3 is a sectional view showing the structure of the optical semiconductor substrate 3 of the present invention. The substrate for optical semiconductor 3 of the present invention is obtained by sequentially forming a metal layer 6, a solder layer 7, and a protective layer 8 made of Au (gold) or Ag (silver) on an insulating ceramic substrate 5. .

  The insulating ceramic substrate 5 used in the present invention is mainly composed of, for example, one selected from aluminum nitride, silicon nitride, silicon carbide, beryllium oxide and diamond. The thermal conductivity of the insulating ceramic substrate 5 is 80 W from the viewpoint of improving heat dissipation when an optical semiconductor such as a laser diode is mounted, suppressing the generation of stress, and suppressing the generation of crystal defects in the optical semiconductor. / M · K or higher, preferably 190 W / m · K or higher.

  The thickness of the insulating ceramic substrate 5 is not particularly limited, and can be appropriately adjusted in consideration of the thermal conductivity, strength, etc. of the insulating ceramic substrate 5, but for example, 0.1 mm or more, 1.5 mm The following range is preferable.

  Further, from the relationship with the thermal conductivity, when the thermal conductivity of the insulating ceramic substrate 5 is K (W / m · K) and the thickness of the insulating ceramic substrate 5 is t (mm), the ratio ( K / t) is preferably 700 or more. That is, it is possible to further improve the heat dissipation of the optical semiconductor substrate 3 by increasing the thermal conductivity K and decreasing the plate thickness t.

  For example, when an aluminum nitride substrate having a thermal conductivity of 200 W / m · K is used, its thickness t is preferably 0.286 mm or less, and aluminum nitride having a thermal conductivity of 170 W / m · K. When a substrate is used, the thickness t is preferably 0.243 mm or less.

  Such an insulating ceramic substrate 5 is formed, for example, by adding a sintering aid to a raw material powder such as aluminum nitride as described above, adding a binder or the like, mixing, and then forming the substrate into a predetermined substrate shape. It is obtained by sintering the body. Various metal compounds can be used as the sintering aid, but rare earth oxides are preferably used.

Examples of rare earth oxides include Y ₂ O ₃ (yttrium oxide), Er ₂ O ₃ (erbium oxide), Yb ₂ O ₃ (ytterbium oxide), and among these, Y ₂ O ₃ is particularly preferable. Used.

In addition to rare earth oxides, oxides of alkaline earth metal elements such as Ca, Ba and Sr, Si compounds such as SiO ₂ and Si ₃ N ₄ , B ₂ O ₃ , B ₄ C, TiB ₂ and LaB A boron compound such as ₆ may be used in combination. In addition, you may mix | blend rare earth oxide, an alkaline-earth metal oxide, etc. as carbonate, oxalate, nitrate, fluoride etc. which become an oxide at the time of baking.

  Further, for a sintered body having translucency such as aluminum nitride, for example, coloring of W, Ti, Zr, Hf, Cr, Mo, Sr, etc. in order to suppress the characteristic change due to re-reflection of the laser beam. Chemicals may be added.

  In this case, the coloring material is preferably added in a proportion of 5.0% by weight or less with respect to the aluminum nitride raw material powder or the like. If the added amount of the coloring material is too large so as to exceed 5.0% by weight, the thermal conductivity of the sintered body tends to be lowered, and the heat dissipation of the optical semiconductor substrate 3 is impaired.

  The colorant is preferably added as an oxide, nitride, or fluoride of the above various elements, and the form is a characteristic of the insulating ceramic substrate 5 such as heat dissipation and strength. It is preferable to select arbitrarily in consideration of the influence on

  A metal layer 6 is provided on the insulating ceramic substrate 5 as described above. For example, the metal layer 6 is laminated in the order of a Ti layer, a Pt layer, and an Au layer from the insulating ceramic substrate 5 side. A circuit may be formed on the metal layer 6 or a circuit may not be formed. The total thickness of the metal layer 6 made of such a Ti layer, Pt layer, Au layer or the like is preferably 3 μm or less.

  The Ti layer, the Pt layer, and the Au layer are formed on the insulating ceramic substrate 5 by PVD (Physical Vapor) such as sputtering, vacuum deposition, molecular beam epitaxy (MBE), ion plating, and laser deposition. It is preferable to apply a thin film formation method such as a CVD (Chemical Vapor Deposition) method such as a deposition (physical vapor deposition) method, or a CVD method such as a thermal CVD method, a plasma CVD method, or a photo CVD method. .

  A solder layer 7 is formed on the metal layer 6. The solder layer 7 is made of Sn alone, or made of an Au—Sn alloy or Au—Sn mixture containing 50% by weight or more of Sn and the balance being substantially Au.

  By including 50% by weight or more of Sn in the solder layer 7, the hardness of the solder layer 7 can be effectively reduced. This sufficiently relaxes the stress generated mainly by the difference in thermal expansion coefficient between the insulating ceramic substrate 5 and the optical semiconductor when bonding the optical semiconductor or during subsequent use, and crystal defects are generated even by a slight stress. Then, the generation of crystal defects in the optical semiconductor whose lifetime is shortened can be suppressed and the lifetime can be increased.

  The solder layer 7 is more preferably a single substance of Sn or 60% by weight or more of Sn and the balance is made of Au, and more preferably a simple substance of Sn or 70% or more of Sn of the balance is made of Au. The melting point of the solder layer 7 is preferably 210 ° C. or higher and 500 ° C. or lower, and more preferably 210 ° C. or higher and 400 ° C. or lower.

  By increasing the Sn content in this way, the hardness of the solder layer 7 can be reduced more effectively, and the stress applied to the optical semiconductor can be sufficiently relaxed when the optical semiconductor is joined or during subsequent use. Even when a slight stress is applied, crystal defects are generated and the lifetime is shortened, so that the generation of crystal defects in the optical semiconductor can be suppressed and the lifetime can be extended.

  The solder layer 7 is formed on the metal layer 6 by, for example, a technique such as vacuum deposition or sputtering of Au or Sn, or by a technique of applying a solder paste having the above-described composition using a screen printing method or the like. be able to. The thickness of the solder layer 7 is preferably 2 μm or more and 5 μm or less.

  If the thickness of the solder layer 7 is 2 μm or less, since the thickness of the solder layer 7 is too thin, the stress generated due to the difference in thermal expansion coefficient between the optical semiconductor and the insulating ceramic substrate 5 cannot be sufficiently relaxed. There is a possibility that it is difficult to suppress the generation of crystal defects in the semiconductor and extend the life. Further, if the thickness of the solder layer 7 is about 5 μm, a sufficient buffering effect can be obtained, and providing more than that is not preferable from the viewpoint of productivity and the like, and on the other hand, suppressing the generation of crystal defects in the optical semiconductor. It is not preferable because the effect may be reduced and the life may be shortened.

  A protective layer (hereinafter simply referred to as a protective layer) 8 made of Au or Ag is formed on the solder layer 7 as described above. This protective layer 8 is provided in order to prevent an oxide film from being formed on the surface of the solder layer 7. The solder layer 7 according to the present invention has a Sn content of 50% by weight or more in order to minimize the stress applied to the optical semiconductor when joining the optical semiconductor or during subsequent use, to suppress the generation of crystal defects and to prolong the life. The hardness is reduced by including.

  However, since the content of Sn that is easily oxidized is large, an oxide film is easily formed on the surface. This oxide film reduces the solder wettability and makes it difficult to join the optical semiconductor. Also, after joining the optical semiconductor, the thermal resistance is high, so that the heat transfer from the optical semiconductor to the insulating ceramic substrate 5 is hindered. Crystal defects are generated in the optical semiconductor to shorten the lifetime.

  Therefore, in the present invention, the protective layer 8 made of Au or Ag is provided to prevent the formation of the oxide film in the solder layer 7. Since the protective layer 8 is made of Au or Ag, which is a metal that is difficult to oxidize, the formation of the oxide film in the solder layer on which the oxide film is easily formed as described above can be suppressed, and the decrease in solder wettability can be suppressed. . In addition, Au or Ag constituting the protective layer 8 can form a eutectic with Sn, which is a component of the solder layer, so that it easily mixes with the solder layer 7 at the time of joining the optical semiconductor and hardly causes adverse effects.

  The thickness of such a protective layer 8 is 0.01 μm or more and 1 μm or less. When the thickness of the protective layer 8 is less than 0.01 μm, a portion where the surface of the solder layer 7 is not sufficiently covered by the protective layer 8 is generated, and this uncovered portion is oxidized to become an oxide film. Difficult to join semiconductors. In addition, after the optical semiconductor is bonded, the heat resistance of the oxide film is high, so that the heat transfer from the optical semiconductor to the insulating ceramic substrate 5 is hindered, crystal defects occur in the optical semiconductor, and the lifetime is shortened. .

  If the thickness of the protective layer 8 exceeds 1 μm, the protective layer 8 and the solder layer 7 are not completely mixed during the heat treatment for bonding the optical semiconductor, and the protective layer 8 remains, and Au or Ag In some cases, a portion having a high concentration of is produced, and it becomes difficult to join the optical semiconductor. Further, after bonding of the optical semiconductor, the portion where the protective layer 8 remains or the portion where the concentration of Au or Ag is high is hard, so that the stress is not sufficiently relieved, crystal defects occur in the optical semiconductor, and the lifetime is increased. Shorter.

  The thickness of the protective layer 8 is more preferably 0.01 μm or more and 0.2 μm or less. By setting the thickness of the protective layer 8 to 0.2 μm or less, the protective layer 8 can be easily mixed with the solder layer 7 during the heat treatment for bonding the optical semiconductor, and the concentration of Au or Ag is also reduced. It is possible to suppress a partial increase, and by sufficiently relaxing the stress, generation of crystal defects in the optical semiconductor can be suppressed and the life can be extended.

  Such a protective layer 8 made of Au or Ag is formed by PVD (Physical Vapor Deposition) methods such as sputtering, vacuum deposition, molecular beam epitaxy (MBE), ion plating, and laser deposition. In some cases, it may be formed by using a thin film forming method such as a CVD (Chemical Vapor Deposition) method such as a thermal CVD method, a plasma CVD method, a photo CVD method, or a paste method. It may be formed.

  Such an optical semiconductor substrate 3 of the present invention is used as a semiconductor laser element by bonding an optical semiconductor. The optical semiconductor substrate 3 and the optical semiconductor are preferably joined at a temperature higher than the melting temperature of the solder layer 7, for example, 250 ° C. or higher and 400 ° C. or lower for 10 seconds or longer and 5 minutes or shorter. The substrate 3 for optical semiconductors of the present invention is suitably used particularly for bonding high-output type optical semiconductors. When a high-output type optical semiconductor is bonded, the light density at the end face of the optical semiconductor becomes excessive during use, so that a large amount of heat is likely to be generated, and excessive stress is easily applied to the optical semiconductor. This stress causes crystal defects in the optical semiconductor and shortens the lifetime. For this reason, the optical semiconductor substrate 3 of the present invention can greatly extend the life compared to the prior art by bonding such a high output type optical semiconductor.

  The present invention will now be described in more detail with reference to examples.

  A Ti, Pt, Au film is sequentially formed on an aluminum nitride substrate having a length of 1.0 mm, a width of 1.0 mm, and a thickness of 0.2 mm by using a vacuum evaporation method to form a metal layer having a thickness of 0.6 μm as a whole. A solder layer made of Sn alone or Sn and Au was formed on the metal layer, and an Au layer as a protective layer was further formed on the solder layer using a vacuum deposition method to obtain an optical semiconductor substrate.

  As shown in Table 1, the optical semiconductor substrate changes the Au—Sn composition of the solder layer and changes the thickness of the Au layer formed on the solder layer in the range of 0.008 to 1.2. Several types were manufactured.

  Further, in order to investigate the influence of the difference in thermal conductivity of the aluminum nitride substrate, the thermal conductivity of the aluminum nitride substrate is 70, 170, 200, 250 (with the solder layer composition of Au 10 wt% and Sn 90 wt%). W / m · K) and the same experiment was conducted.

  Furthermore, in order to investigate the influence of the difference in the thickness of the solder layer, the composition of the solder layer is 10 wt% Au, 90 wt% Sn, the thermal conductivity of the aluminum nitride substrate is 200 (W / m · K), the thickness of the Au layer An experiment was conducted with a thickness of 0.1 μm by changing the thickness of the solder layer in the range of 1 μm to 6 μm.

  In order to examine the effectiveness of the Ag layer as a protective layer, the composition of the solder layer is Au 10 wt%, Sn 90 wt%, the thermal conductivity of the aluminum nitride substrate is 200 (W / m · K), the thickness of the solder layer An experiment was conducted with a thickness of 3 μm by changing the thickness of the Ag layer as the protective layer.

  In Table 1, those marked with “*” are within the scope of the present invention, the Sn content in the solder layer is 50% by weight or more, and the thickness of the Au layer or Ag layer is 0.01 μm or more. 1 μm or less.

  Next, a laser diode having a length of 1.0 mm, a width of 1.0 mm, and a thickness of 0.2 mm is placed on the optical semiconductor substrate and bonded by performing a heat treatment at 400 ° C. for 1 minute. Produced. Then, in order to examine effects such as the composition of the solder layer and the thickness of the Au layer or Ag layer as a protective layer formed on the solder layer, the thermal resistance ratio and the Iop life were measured. Table 1 shows the measurement results of the thermal resistance ratio and the Iop life.

  The thermal resistance ratio was measured by measuring the thermal resistance when the pulse time was 1 s, and the result was the thermal resistance when the composition of the solder layer was 20 wt% Au, 80 wt% Sn, and the thickness of the Au layer was 0.1 μm. Was expressed as a ratio (%). The thermal resistance ratio is related to the evaluation of solderability, and those with a high thermal resistance ratio have a portion where oxidation occurs on the surface of the solder layer, or the Au layer or Ag layer as a protective layer completely dissolves in the solder layer. Indicates that there is a part that is not.

The Iop life was measured by emitting a current of 30 mA in a state where the semiconductor laser element was placed in a constant temperature bath at 80 ° C. to emit light, and then measuring the time until no light was emitted. The longer the Iop life, the more the stress applied to the laser diode is relaxed or the better the soldering.

  As is apparent from Tables 1 and 2, the Sn content in the solder layer is 50% by weight or more, and the thickness of the Au layer as the protective layer is 0.01 μm or more and 1 μm or less. It was confirmed that the stress applied to the laser diode was relaxed over time, and the generation of crystal defects in the laser diode was suppressed. Moreover, it was confirmed that the Iop life can be further improved by setting the Sn content in the solder layer to 60 wt% or more, and further to 70 wt% or more.

  Furthermore, among these, the Au layer having a thickness of 0.01 μm or more and 0.2 μm or less as the protective layer has a long Iop life, and the aluminum nitride substrate has a thermal conductivity of 80 W / m · K or more, Furthermore, it was confirmed that those using 190 W / m · K or more have a longer Iop life. Further, it was confirmed that the same effect as that of the Au layer can be obtained when the Ag layer is used as the protective layer.

  The present invention can be applied to the business of manufacturing a semiconductor laser element by joining optical semiconductors.

Claims (4)

An insulating ceramic substrate;
A metal layer provided on the insulating ceramic substrate;
A solder layer which is provided on the metal layer and contains Sn alone or Sn in an amount of 50% by weight or more, with the balance being substantially Au;
An optical semiconductor substrate comprising: a protective layer made of Au or Ag having a thickness of 0.01 μm or more and 1 μm or less provided on the solder layer. The optical semiconductor substrate according to claim 1,
An optical semiconductor substrate, wherein the solder layer has a thickness of 2 μm or more and 5 μm or less. The optical semiconductor substrate according to claim 1,
A substrate for an optical semiconductor, wherein the insulating ceramic substrate is mainly composed of one selected from aluminum nitride, silicon nitride, silicon carbide, beryllium oxide and diamond. The substrate for optical semiconductors according to claim 3,
An optical semiconductor substrate, wherein the insulating ceramic substrate has a thermal conductivity of 80 W / m · K or more.

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